An icon button with no name, a form field with only a placeholder or a removed focus outline locks screen reader and keyboard users out of your site, and these are the failures accessibility audits and complaints start with. This skill finds those and eleven other common WCAG failures in your HTML and CSS, and tells you how to fix each one.

Your agent runs a scanner on your .html pages and .css files. It parses the HTML (comments skipped, exact line numbers), works out each button's and link's accessible name from text, hidden text, aria-label and image alt, and each field's label from <label for>, a wrapping label or ARIA attributes. Template code ({{ }}, {% %}) counts as present. It never opens a browser. It returns BLOCK, REVIEW, or NOT FLAGGED, with the file, line, reason, and a safer approach.

What it checks

BLOCK (fix before shipping)

• A01: images without alt text

• A02: form fields without a label (placeholder only)

• A03: buttons and links with no accessible name

• A04: no page language on <html>

• A05: click handlers on divs and spans the keyboard cannot reach

REVIEW (check before release)

• A11: positive tabindex

• A12: pinch zoom turned off

• A13: skipped heading levels

• A14: iframes without a title

• A15: autoplaying video or audio with sound

• A16: duplicate ids

• A17: aria-hidden on focusable elements

• A18: data tables without header cells

• A19: focus outlines removed in CSS

What's included

• The scanner (Python 3.9+, standard library only)

• A rules guide with the reason, the WCAG criterion and a safer approach for each rule

• A risky and a safe example page with CSS, and the real report the scanner produces on the risky one

Limits

It reads each file as written, not the page a browser builds: content added by JavaScript frameworks, colour contrast, captions and screen reader behaviour still need a manual test. Automated checks find only part of all accessibility problems. NOT FLAGGED is not a guarantee.

Contents

One ZIP file with 9 files: SKILL.md, the scanner in scripts/ (2 Python files), references/rules.md (every rule with its reason and safer approach), and examples/ (4 example files plus report.md, the real scanner output on the risky example).

How to use: This is an agent skill: a folder with a SKILL.md file and Python scripts that an AI coding agent such as Claude Code, Cursor, or Codex CLI can run. Unzip it into your agent's skills folder (for Claude Code: ~/.claude/skills/), then ask your agent to check your project. The scripts also run on their own with Python 3.9 or newer, with nothing to install. They read your files only: no network access, and nothing is sent anywhere.